1. Field of the Invention
The present invention relates to, in particular, a developing apparatus mounted in an image forming apparatus that visualizes an electrostatic latent image with a developing agent including toner, the electrostatic latent image being formed on an image bearing member by electrophotography, an electrostatic recording method, or the like.
2. Description of the Related Art
An image forming apparatus using electrophotography according to the related art includes a developing apparatus that forms a toner image of an electrostatic latent image formed on a photosensitive member that serves as an image bearing member. The toner image is formed with toner included in a developing agent.
A most general developing apparatus includes a developing-agent container that contains the developing agent; a conveying member that conveys the developing agent contained in the developing-agent container while stirring and mixing the developing agent; a developing-agent bearing member that bears the developing agent and conveys the developing agent to a section that faces the photosensitive member; and a layer-thickness regulating member that regulates an amount of the developing agent on the developing-agent bearing member.
Here, a developing apparatus that uses two-component developing agent including non-magnetic toner and magnetic carrier will be described. The developing agent contained in the developing-agent container is stirred and mixed by a developing screw, which serves as the conveying member, in the developing-agent container. The developing agent is electrically charged as a result of frictional electrification in the stirring and mixing process. The charged developing agent is retained by a developing sleeve, which serves as the developing-agent bearing member, mainly by a magnetic force. A magnet having a plurality of magnetic poles that serves as magnetic-field generating means is disposed in the developing sleeve. The developing sleeve is disposed in a rotatable manner at a position where the developing sleeve faces the photosensitive member. As the developing sleeve rotates, the developing agent is conveyed to a developing area which faces the photosensitive member, and is used in a developing process. In the developing area, a developing bias is applied to the developing sleeve so that the toner included in the developing agent is caused to transfer to an electrostatic latent image formed on the surface of the photosensitive member. As a result, a toner image corresponding to the electrostatic latent image formed on the surface of the photosensitive member.
In the developing apparatus, a regulating blade, which serves as the layer-thickness regulating member, is generally disposed so as to face an outer peripheral surface of the developing sleeve with a predetermined gap provided therebetween. Various types of regulating blades, such as a magnetic plate, a non-magnetic plate, a combination of a magnetic plate and a non-magnetic plate, an elastic body, etc., have been proposed and put into practical use. In the process of conveying the developing agent retained by the developing sleeve to the developing area, the amount of developing agent conveyed to the developing area is regulated when the developing agent passes through the gap between the developing sleeve and the blade. Thus, an adjustment is made so that a stable amount of developing agent is supplied. One of the magnetic poles of the magnet (called a cutting pole) is disposed so as to face the regulating blade, so that the amount of developing agent is regulated while an accumulation of the developing agent is provided. With this structure, a certain amount of developing agent can be continuously accumulated at a section immediately upstream of the regulating blade. Therefore, the developing agent can be stably supplied to the developing sleeve.